Rapportive is a Firefox plug-in that replaces the ads in Gmail with detailed, Web-sourced information about the sender of each message in your inbox.

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Tim Ferriss, author of The 4-Hour Workweek says the trick with e-mail is knowing more information about who’s messaging you so you don’t waste time researching them to figure out if they’re worth responding to. Ferriss uses rapportive.com, a Firefox plug-in which replaces the ads in Gmail with detailed, web-sourced information about the sender of each message in your inbox. “I get a 15 to 20 percent time savings from this one plug-in alone,” he says.